The present invention relates to techniques for preventing vibrations of a head suspension assembly used in a rotary disk storage device, such as a magnetic disk device or an optical disk device, and more particularly, to a technique for preventing fluttering of the head suspension assembly resulting from an air flow generated on a surface of a rotating disk.
In the rotary disk storage device, a disk as a recording medium is rotated at a high speed to generate an air flow on a surface thereof. This gives a slider mounted with a head for reading and writing data an ascending force, resulting in the slider floating above the surface of the disk. While data is being read or written, the air flow generated on the surface of the disk collides with an actuator arm, a load beam, a flexure, the slider, and the like located above the surface of the disk, producing an oscillation called a fluttering in these components.
Fluttering must be suppressed as much as possible, since fluttering eventually gives the slider irregular oscillations, thus degrading a servo control function for a tracking operation. Examples of conceivable various portions that could cause fluttering resulting from the effect of an air flow include an opening defined in a load beam. Fluttering caused by this opening is described in, for example, Japanese Patent Laid-open No. 2002-279745.
With the recent trend toward a greater recording capacity of disks, a track pitch has become narrower and narrower. This calls for an even greater performance in tracking operations of the head. As a result, a need arises for taking measures against types of fluttering that have not so far presented any big problems.
FIG. 1 shows a state in which wires are supported in a conventional actuator head suspension assembly 10. The actuator head suspension assembly 10 includes an actuator assembly and head suspension assemblies 18a to 18f connected to the actuator assembly. The actuator assembly is composed of a pivot bearing 11, a coil support 14, a voice coil 16, and actuator arms 12a to 12d. Each of the head suspension assemblies 18a to 18f is composed of a load beam, a flexure, and a slider (not shown). The slider is mounted to the flexure at a leading end portion of the head suspension assembly and a head is attached to the slider.
Four actuator arms 12a to 12d are laminated one on top of another. One head suspension assembly is attached to each of the topmost actuator arm 12a and the bottom actuator arm 12d. Two head suspension assemblies are attached to each of the two actuator arms 12b, 12c laminated on an inner side between the topmost and bottom actuator arms 12a, 12d. 
Wire support members 13a to 13d each having a slit formed therein are respectively mounted to the respective side faces of the actuator arms 12a to 12d. Wires connected to the associated heads are inserted and secured in the slits of the wire support members on the side faces of the actuator arms 12a to 12d, being led to a position near the pivot bearing 11.
First of all, terminology relating to the actuator arm applicable throughout this specification will be explained with reference to FIG. 13. FIG. 13 is a diagram illustrating schematically an actuator arm 500 as viewed from a head side, and represents a cross section taken along the same line as that of the actuator arm 12a in FIG. 1 taken along arrows A—A.
A face 501 and a face 503 are faces located in a vertical direction of a device when the actuator arm is actually mounted in the device, each of the faces being referred to as a front surface. A face 505 and a face 507 are side faces located in a rotating direction of the actuator assembly. The face 505 is a surface close to the disk when the actuator arm is actually mounted in the device, being referred to as an inner side surface. The face 507 is a surface close to a side wall of a housing, being referred to as an outer side surface. The interval between the front surface 501 and the front surface 503 is referred to as an actuator arm thickness.
A face 509 divides the actuator arm thickness defined by the front surface 501 and the front surface 503 into two, being referred to as a central surface. An up-and-down direction indicated by arrows X running substantially perpendicular to the central surface is referred to as a vertical direction. A right-and-left direction indicated by arrows Y running substantially perpendicular to the outer side surface or the inner side surface is referred to as a lateral direction. A direction perpendicular to the cross section shown in FIG. 13 is referred to as a longitudinal direction of the actuator arm or the actuator head suspension assembly. This longitudinal direction may also be used in terms of the wire support member. Incidentally, the front surface, outer side surface, and inner side surface of the actuator assembly may not necessarily be a flat surface in a strict sense of the word. These surfaces may have projections and depressions, or may have slants and curvatures. In addition, when referring to the actuator head suspension assembly in the longitudinal direction, a side of the head is referred to as a leading end side, while a side of the pivot bearing is referred to as a supporting end side. The same terminology is used to refer to positional relations of the wire support member and the head suspension assembly, as may be necessary.
FIG. 2(A) is a schematic cross-sectional view taken along arrows A—A in FIG. 1 as viewed from the leading end side. FIG. 2(A) illustrates the wire support members 13a to 13d mounted, respectively, on the outer side surfaces of the actuator arms 12a to 12d. A slit provided with a face open in the lateral direction is formed in each of the wire support members 13a and 13d. Similarly, two slits, each having the same face open in the lateral direction as that formed in each of the wire support members 13a and 13d, are formed in each of the wire support members 13b and 13c. Wires 20a to 20f are inserted and secured in the associated slits.
A back surface located opposite to the slit open surface of each wire support member is bonded to the outer side surface of each of the corresponding actuator arms. Air generated from a rotating disk flows to the two front surfaces of each actuator arm. The wires 20a to 20f can never be affected by the air flow to develop fluttering, since the wires 20a to 20f are inserted and secured in the slits of the wire support members 13a to 13d as evident from FIG. 2(A).
FIG. 2(B) is a schematic cross-sectional view taken along arrows B-B in FIG. 1 as viewed from the leading end side. The wire support members are not formed in the cross section shown in FIG. 2(B) for the following reason. The wires 20a to 20f are not given a support from the outer side surface of the actuator arms, thus floating in the air.
In the head suspension assembly, the wire is connected to the head, the head is mounted on the slider, the slider is mounted on the flexure formed of a sheet material, the flexure is laminated on a surface of the load beam, and the load beam is laminated on a surface of the actuator arm. Since the wire is supported by the flexure or the load beam in the head suspension assembly, the wire is disposed in the vertical direction at a position farther away from the central surface in the vertical direction with respect to a plane including the front surface of the actuator arm.
In the B—B section, therefore, the position of the wire is away from the central surface to reach a point near the front surface of the actuator arm. This makes it impossible or difficult to form the wire support member provided with a slit or slits. Being flexible, the wire can be inserted and secured in the slit formed in the wire support member at the location of the A—A section. The wire cannot, however, be secured in the slit at the location near the B—B section which is close to the head suspension assembly. The wire is, in this case, in an aerial position.
As a result, air flowing from a direction of the inner side surface of the actuator arm along the front surface thereof forms a swirl immediately after the air has moved past the outer side surface of the actuator arm as shown in FIG. 3. This swirl gives the wire 20a oscillations in the vertical direction as shown by arrows X, that is, what is called a fluttering phenomenon. Since the wire 20a extends toward the leading end side of the head suspension assembly, and is secured to the load beam and the flexure and further to the slider, the oscillations are given to these components and consequently to the slider.
The wire support member 13a of the FIG. 2(A) has two vertical front surfaces 15, 17 (hereinafter referred to as “outer front surfaces”). The distance between the outer front surface 15 and the outer front surface 17 is referred to as a thickness of the wire support member. Referring to FIG. 2 (A), the thickness of the wire support member 13a is substantially equal to a thickness of the actuator arm 12a. A method could be conceivable in which at the location of the B—B section the thickness of the wire support member is increased to secure the wire in position and the slit is formed up to a point near the head suspension assembly. It is however necessary that the actuator arm be turned with a slight gap kept from the surface of the disk. This puts limitations on the thickness of the wire support member. Furthermore, if there is provided an excessively large step in a boundary between the wire support member and the actuator arm, the air flow is disturbed at a portion of the step, thus increasing the occurrence of fluttering in the actuator arm.
Another method could be conceivable in which the wire is bonded onto the front surface of the actuator arm, whereby the wire is secured up to a point near the head suspension assembly. This method, however, makes it difficult to remove and replace the head suspension assembly, should a fault be found as a result of an operation test carried out after the head suspension assembly has been mounted to the actuator assembly.
Still another conceivable method is to form a support structure such as a bracket integral with the actuator arm by molding on the outer side surface of the actuator arm. Since the actuator arm is disposed so that the inner side surface thereof is extremely close to the disk, it is difficult to widen both the inner side surface and the outer side surface in the lateral direction. Forming a bracket extending in the lateral direction only on the outer side surface for supporting the wiring destroys symmetry of the actuator assembly, which is not favorable in terms of operating characteristics.
Further, the wire support member may be extended further toward the leading end side, while keeping the same shape as that shown in FIG. 2(A) in an attempt to shorten the length of the portion of the wire not supported and running aerially. In this case, it is necessary that the wire be displaced abruptly so as to leave the central surface for a portion of the wire from where it comes out of the slit in the wire support member to where it is secured to the head suspension assembly. This not only makes it difficult to insert the wire in the slit, but also increases a possibility of the wire being damaged due to a rise in contact pressure between the wire and an entrance of the slit. In addition, an abrupt displacement could degrade functions of the wire.
It was therefore desired that a new wire support member be invented using the basic construction of the wire support member shown in FIG. 1 and preventing fluttering from occurring in the wire at portions where no slits can be formed.